The present invention relates to an electronic apparatus having a standby state and a normal state, and particularly to an electronic apparatus that can reduce power consumption in the standby state.
FIG. 4 is a diagram of assistance in illustrating operation of a conventional subscription satellite broadcasting receiver.
Reference numeral 10 denotes a satellite broadcasting receiver; reference numeral 20 denotes a broadcasting station; reference numeral 30 denotes a satellite; reference numeral 4 designates an IC card; reference numeral 5 designates an antenna device; reference numeral 51 indicates a receiving antenna; reference numeral 52 indicates a low-noise frequency converter circuit; reference numeral S6 denotes a feed line; reference numeral S7 denotes a program purchase signal; reference numeral S8 indicates an apparatus operation signal; and reference numerals S11 and S12 each indicate a radio wave signal.
The apparatus operation signal S8 is for example a signal inputted from an external remote control to the satellite broadcasting receiver 10 by means of infrared rays or the like. The satellite broadcasting receiver 10 is operated by this signal. The apparatus operation signal S8 includes a signal for setting the satellite broadcasting receiver 10 to a normal state or a standby state.
The feed line S6 is an electric wire for the satellite broadcasting receiver 10 to supply an operating voltage to the antenna device 5. In addition to the voltage, the feed line S6 transmits a signal received and generated by the antenna device 5 to the satellite broadcasting receiver 10.
The antenna device 5 receives and amplifies a radio wave signal S12 sent from the satellite 30, then converts the resulting signal into an intermediate frequency, and transmits the result to the satellite broadcasting receiver 10. The voltage for operating the antenna device 5 is supplied from the satellite broadcasting receiver 10 through the feed line S6.
The antenna device 5 includes the receiving antenna 51 and the frequency converter circuit 52.
The receiving antenna 51 receives the radio wave signal S12 sent from the satellite 30 and concentrates the signal onto the low-noise frequency converter circuit 52.
The low-noise frequency converter circuit 52 amplifies the concentrated radio wave signal by means of a low-noise amplifier, converts the resulting signal into an intermediate frequency, and transmits the result to the satellite broadcasting receiver 10 through the feed line S6. A power supply voltage to be supplied to the low-noise frequency converter circuit 52 is supplied from the satellite broadcasting receiver 10 through the feed line S6. The radio wave signal S12 sent from the satellite 30 is generated by multiplexing two polarized waves such as a vertically polarized wave and a horizontally polarized wave that have the same frequency and do not affect each other. The frequency converter circuit 52 includes two circuits for receiving the two polarized waves. The frequency converter circuit 52 enables either one of the two circuits according to a supplied voltage to thereby output a signal converted into an intermediate frequency to the satellite broadcasting receiver 10. Thus, the satellite broadcasting receiver 10 can choose which of the polarized waves to receive by switching the voltage supplied to the frequency converter circuit 52 between two levels, for example 11V and 15V.
The IC card 4 includes information on a subscriber to subscription satellite broadcasting, subscription information on a purchased program and the like recorded thereon. The viewer is allowed to view a program by inserting the IC card 4 into the satellite broadcasting receiver 10 and having the satellite broadcasting receiver 10 read the information recorded on the card. Subscription information on a newly purchased program is written on the IC card 4 by the satellite broadcasting receiver 10.
The program purchase signal S7 is transmitted from the satellite broadcasting receiver 10 to the broadcasting station 20. More specifically, information on a satellite broadcasting subscriber, information on a program to be purchased and the like recorded on the IC card 4 are sent from the satellite broadcasting receiver 10 to the broadcasting station 20 via a telephone line or the like.
Incidentally, the IC card 4 may be replaced with various recording media that allow writing and reading of information.
After receiving the program purchase signal S7 from the satellite broadcasting receiver 10, the broadcasting station 20 superimposes on a radio wave signal S11 program information being broadcast and subscription information necessary for the viewer to view the purchased program on the satellite broadcasting receiver 10, and then sends the radio wave signal S11 to the satellite 30.
The satellite 30 receives the radio wave signal S11 from the broadcasting station 20, and then sends a radio wave signal S12 to the earth.
The satellite broadcasting receiver 10 is operated externally, or for example switched between a standby state and a normal state by being supplied with an apparatus operation signal S8. The satellite broadcasting receiver 10 reads and writes information on the inserted IC card 4. Information read from the IC card 4 by the satellite broadcasting receiver 10 and information on program purchase inputted from the apparatus operation signal S8 are transmitted to the broadcasting station 20 by a program purchase signal S7. The satellite broadcasting receiver 10 supplies a voltage to the antenna device 5 through the feed line S6, and also receives a signal including program information and subscription information that has been received and frequency-converted by the antenna device 5.
Operation of the satellite broadcasting receiver 10 configured as described above will next be described.
When a power switch, not shown in the figure, of the satellite broadcasting receiver 10 is turned on, a power supply voltage for the low-noise frequency converter circuit 52 is supplied to the antenna device 5 via the feed line S6. Operated by the power supply voltage, the low-noise frequency converter circuit 52 converts the radio wave signal S12 from the satellite 30 into an intermediate frequency, and then transmits the result to the satellite broadcasting receiver 10 through the feed line S6.
When the IC card 4 is inserted into the satellite broadcasting receiver 10, information on a subscriber, subscription information on a purchased program and the like recorded on the IC card 4 are inputted into the satellite broadcasting receiver 10. In order for the viewer to view a program received by the satellite broadcasting receiver 10 on an image display apparatus and a speaker not shown in the figure, the IC card needs to be inserted in the satellite broadcasting receiver 10 in a readable state and subscription information on the program to be viewed needs to be recorded on the IC card 4.
A case in which an instruction to newly purchase a program is provided will be described.
When an apparatus operation signal S8 instructs the satellite broadcasting receiver 10 to newly purchase a program, information on a subscriber and information on the program to be purchased, which are read from the IC card 4, are sent as a program purchase signal S7 to the broadcasting station 20 via a telephone line. Timing of sending the program purchase signal S7 to the broadcasting station 20 is synchronized with a given signal sent irregularly by the radio wave signal S11 and the radio wave signal S12 from the satellite 30.
The broadcasting station 20 generates subscription information for allowing the specific subscriber specified by the received program purchase signal S7 to view the specific program specified by the program purchase signal S7. The broadcasting station 20 superimposes the subscription information upon the radio wave signal S11 together with program information being broadcast, and then transmits the signal to the satellite 30. Receiving the radio wave signal S11, the satellite 30 sends a radio wave signal S12 to the earth.
Receiving the radio wave signal S12, the receiving antenna 51 concentrates the radio wave signal S12 onto the low-noise frequency converter circuit 52. The low-noise frequency converter circuit 52 converts the radio wave signal S12 into an electric signal to flow therein, then amplifies the signal by means of a low-noise amplifier, converts the amplified signal into an intermediate frequency, and then transmits the result to the satellite broadcasting receiver 10 through the feed line S6.
The satellite broadcasting receiver 10 processes the program information and the subscription information received by the feed line S6 to extract subscription information that matches the subscriber information given to the individual IC card 4 and record the subscription information on the IC card 4. The satellite broadcasting receiver 10 allows viewing of the specific program purchased by the viewer only when the subscription information is recorded on the IC card 4.
As described above, the conventional satellite broadcasting receiver 10 shown in FIG. 4 receives subscription information for allowing viewing of the program purchased by the viewer from the broadcasting station 20 via the radio wave signal S12. Timing of sending the program purchase signal S7 to the broadcasting station 20 is synchronized with a given signal sent irregularly by the radio wave signal S12.
When considering a case where the viewer instructs the satellite broadcasting receiver 10 to newly purchase a program by means of an apparatus operation signal S8, however, the satellite broadcasting receiver 10 needs to always wait for a signal sent irregularly from the satellite 30 for providing timing for the program purchase signal S7 and a signal of subscription information. Thus, the satellite broadcasting receiver 10 needs to supply voltage to the antenna device 5 at all times. Also, in this case, a circuit not shown in the figure for processing received signals and a circuit not shown in the figure for processing information on the IC card and sending a program purchase signal S7 to the broadcasting station 20, which circuits are included in the satellite broadcasting receiver 10, need to be kept operating. Therefore, even when the operating state of the satellite broadcasting receiver 10 is changed from a normal state for performing normal operation to a standby state for reducing power consumption by stopping the normal operation, these circuits consume power. Thus, standby power consumed by the electronic apparatus in the standby state is for example about 10 W, which is greater than that of other electrical household appliances.
Moreover, in order to select the type of polarized wave to be received, the satellite broadcasting receiver 10 needs to change the voltage supplied to the antenna device 5. Accordingly, in cases where a single antenna device is shared by a plurality of satellite broadcasting receivers, it is possible that the satellite broadcasting receivers select polarized waves different from each other. Therefore, if the feed line is simply distributed to the satellite broadcasting receivers, the voltage supplied to the antenna device 5 cannot be fixed, so that the satellite broadcasting receivers cannot properly receive a radio wave signal from the broadcasting satellite.